In recent years, attempts have been actively made in fields such as drug discovery to find molecules having specific interaction with a certain specific molecule by utilizing intermolecular interaction. Specifically, immobilizing a molecule (probe molecule) having interaction on a support, and trapping and purifying another molecule (target material) by utilizing a specific interaction is widely carried out.
For example, the discovery of the intracellular binding protein FKBP12 of the immunosuppressant FK506 using an affinity resin (Nature, 341, 758, 1989) has been known. A porous gel such as agarose is commonly used as such affinity resin. However, when using a porous gel, the so-called phenomenon nonspecific adsorption in which molecules other than the target molecule are adsorbed on the affinity resin arises and thus, the problem that separation and purification of the target molecule is difficult arises. A certain proportion among the probe molecules bond internally to the porous gel and as a result of such probe molecules having insufficient interaction with the target material, the problem arises that trapping efficiency of the target material is reduced.
As a solution to such nonspecific adsorption, microspheres made from a styrene/glycidyl methacrylate polymer, of which the surface is covered with glycidyl methacrylate, and a biologically-related material bonded to the polymer through a spacer have been proposed (JP-B-3086427 and JP-B-3292721). Also disclosed are particles having a hydrophilic spacer introduced on the surface (WO 2004/025297 A1 and WO 2004/040305A1), and the like. However, none of these have a sufficient effect in lowering nonspecific adsorption. Support particles having still smaller nonspecific adsorption are desired. Also, the efficiency of trapping the target material of these particles is not sufficient.
On the other hand, as biologically-related material carrier polymer particles which are sensitized by a chemical bonding method, carboxyl group-modified polystyrene particles are widely used. However, since the polystyrene particles generally have significant capability of adsorbing other biologically-related materials (nonspecific adsorption) which are not target materials existing in the test sample, the performance of the sensitized particles is inhibited, posing a serious obstacle to use of the particles. In contrast, a blocking method, in which the surface of the particles is first sensitized with the target biologically-active material and a protein having little damage such as bovine serum albumin (BSA) is adsorbed on the remaining particle surface, has difficulty in fully preventing nonspecific adsorption. Also, although it is known that performance of polystyrene particles as biologically-related material carrier particles can be improved by copolymerizing a styrene sulfonate or an acrylic ester having a polyalkylene oxide side chain represented by the formula (CH2CH2O)n or (CH2CHCH3O)m or by hydrolyzing fragments of persulfate initiator bonded to the particles by heat treatment in an alkaline aqueous solution after emulsion polymerization of the particles, the nonspecific adsorption is not sufficiently prevented. Also, the efficiency of trapping the target material of these particles is not sufficient.